Velocity variance reducing multiple bearing arrangement for impeller shaft of centrifugal supercharger

ABSTRACT

A centrifugal supercharger includes a case, a rotatable impeller, a high speed shaft drivingly coupled between the impeller and the engine, and a multiple bearing arrangement rotatably supporting the shaft on the case. The bearing arrangement includes a shaft bearing and a case bearing, each of which includes at least one set of relatively rotatable inner and outer races. The inner race of the shaft bearing is fixed relative to the shaft. The outer race of the case bearing is fixed relative to the case. The outer race of the shaft bearing and inner race of the case bearing are fixed relative to one another either by a spacer or by an integral, unitary construction. In addition, at least one of the bearings can include dual components (inner and outer races and ball rings). The ball rings of the shaft and case bearings can be coplanar to one an other or offset therefrom.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to centrifugal superchargers forproviding increased airflow to an engine. More particularly, the presentinvention concerns a velocity variance reducing multiple bearingarrangement for effectively rotatably supporting the high speed impellershaft of a supercharger, thereby extending bearing life withoutcompromising shaft speed.

2. Discussion of Prior Art

A centrifugal supercharger traditionally has a high speed impeller shaftrotatably supported on the supercharger by two, spaced apart, ballbearings. Given the high rotational speeds of the impeller shaft,commercially available bearings are typically not rated high enough towithstand the demands of a supercharger. Accordingly, the bearing willbe operating outside of its manufacturer recommended limits. That is,there is a substantial risk of bearing failure, thereby limiting theoverall life span of the supercharger.

In response to this undesired limiting risk, some superchargers utilizepaired bearings, i.e. two bearings located in close proximity to oneanother relative to the shaft, (four total bearings) in place of thesingle bearings, with each pair spaced apart from the other pair. This,however, only offers redundancy and while this may offer some slightincrease in bearing life, it is still limiting. This paired arrangementalso has the added disadvantage of a cumulative tolerance effect, or toomuch “slop” for many high precision applications.

OBJECTS AND SUMMARY OF THE INVENTION

Responsive to these and other problems, an important object of thepresent invention is to provide a supercharger that is capable ofproviding relatively high amounts of airflow (e.g., 1800 gasolinehorsepower). It is also an important object of the present invention toprovide a supercharger that has improved durability yet maintains a highload capacity relative to conventional superchargers. In this regard, animportant object of the present invention is to provide a long-lifebearing arrangement for a supercharger capable of generating the desiredhorsepower increases. in addition, an important object of the presentinvention is to provide a bearing arrangement that has virtually nolimiting effect on the boost provided by the supercharger. Anotherimportant object of the present invention is to provide a superchargerhaving a bearing arrangement that assuredly provides sufficient andeffective rotatable support to the high speed impeller shaft. Yetanother important object of the present invention is to provide asupercharger having a durable, simple and inexpensive construction.

In accordance with these and other objects evident from the followingdescription of the preferred embodiments, the present invention concernsa supercharger having a case, a rotatable impeller, a high speed shaftdrivingly coupled between the impeller and a power source, and amultiple bearing arrangement rotatably supporting the shaft on the case.The bearing arrangement includes a shaft bearing and a case bearing,each of which includes relatively rotatable inner and outer races. Theinner race of the shaft bearing is fixed relative to the shaft. Theouter race of the case bearing is fixed relative to the case. The outerrace of the shaft bearing and inner race of the case bearing are fixedrelative to one another. It is believed that such an arrangement reducesthe variances in the velocities of the positive contact points of thebearings, thereby reducing skidding, maximizing both load and speed, andincreasing bearing life. In this manner the present invention provides asupercharger having improved bearing life and same or equal horsepowercapacity, while permitting the use of relatively traditional bearingsthat have been simply and inexpensively modified.

The present invention also involves the use of this bearing arrangementin other applications.

Other aspects and advantages of the present invention will be apparentfrom the following detailed description of the preferred embodiment andthe accompanying drawing figures.

BRIEF DESCRIPTION OF THE DRAWING FIGURES

Several embodiments of the invention are described in detail below withreference to the attached drawing figures, wherein:

FIG. 1 is a fragmentary, partially schematic plan view of an internalcombustion engine including a centrifugal supercharger constructed inaccordance with the principles of the present invention;

FIG. 2 is an enlarged, fragmentary front elevational view of the enginetaken along line 2—2 of FIG. 1;

FIG. 3 is an enlarged cross-sectional view of the supercharger takengenerally along line 3—3 of FIG. 1, particularly illustrating thetransmission chamber and the components located therein;

FIG. 4 is an even further enlarged cross-sectional view of thesupercharger taken generally along line 4—4 of FIG. 3, particularlyillustrating the multiple bearing arrangements supporting the impellershaft;

FIG. 5 is a greatly enlarged, fragmentary cross-sectional view of theimpeller shaft and one of the multiple bearing arrangements;

FIG. 6 is an enlarged, fragmentary cross-sectional view of analternative embodiment of the present invention, wherein the ball ringplanes are offset relative to one another and the exterior dimension ofthe shaft bearing is greater than the interior dimension of the casebearing inner race;

FIG. 7 is an enlarged, fragmentary cross-sectional view of a thirdembodiment of the present invention, wherein the shaft bearing has dualinner and outer races spaced apart from each other and the case bearingis located between the dual races;

FIG. 8 is an enlarged, fragmentary cross-sectional view of a fourthembodiment of the present invention, wherein both the shaft and casebearings has dual races and each ball ring of the shaft bearing isgenerally coplaner with a respective one of the ball rings of the casebearing;

FIG. 9 is an enlarged, fragmentary cross-sectional view of a fifthembodiment of the present invention, which is similar to the embodimentshown in FIG. 7 in the sense that the shaft bearings have dual races,and present an external dimension larger than the internal dimension ofthe case bearing, however, the shaft bearings are located on oppositesides of the case bearing; and

FIG. 10 is an enlarged, fragmentary cross-sectional view of a sixthembodiment of the present invention, wherein the outer race of the shaftbearing and the inner race of the case bearing are integrally formed asa unitary body.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Turning initially to FIG. 1, the supercharger 20 selected forillustration is shown in use with an internal combustion engine 22 of avehicle such as a boat or automobile. Although the illustrated engine 22has eight cylinders, the principles of the present invention are equallyapplicable to various other types of engines. It is noted, however, thatthe supercharger 20 is preferably driven directly by the engine 22, withthe crankshaft 24 and a belt drive 26 providing driving power to thesupercharger 20. Moreover, the supercharger 20 is connected to theengine intake 28 (e.g., an intake plenum box) by a conduit 30, such thatpressurized air generated by the supercharger 20 is directed to theintake 28. Again, the principles of the present invention are notlimited to the illustrated application, but rather the inventivesupercharger 20 may be associated with any system in which a highlypressurized air stream is desired. For example, it is entirely withinthe ambit of the present invention to utilize the supercharger 20 invarious other types of reciprocating engines.

The illustrated supercharger 20 includes a case 32 that definescompressor and transmission chambers as identified hereinbelow. Asperhaps best shown in FIG. 4, the preferred case 32 generally includesthree main sections 34,36,38 that are formed of any suitable material(e.g., polished cast steel) and interconnected as will be described.

The case sections 34 and 36 cooperate to define a compressor chamber 40in which incoming fluid (e.g., air, air/fuel mixture, etc.) ispressurized and accelerated. The case section 34 presents a centralinlet opening 42 (see FIG. 4) through which fluid enters the chamber 40.A filter 44 (see FIG. 1) is preferably provided at the inlet opening 42,as shown, or somewhere upstream from the opening 42. Although notillustrated, the inlet opening 42 may alternatively communicate with aforwardly open conduit (not shown) that extends toward the front of thepowered vehicle, such that air flow to the supercharger 20 isfacilitated when the vehicle is moving in a forward direction. The casesection 34 is configured in such a manner that a portion 40 a of thecompressor chamber 40 extends circumferentially around the inlet opening42 to form a volute of progressively increasing diameter. The voluteportion 40 a of the compressor chamber 40 terminates at a tangentialoutlet opening 46 (see FIGS. 2 and 3), with the latter communicatingwith the engine intake 28 via conduit 30 (see also FIG. 1). In thisregard, fluid entering the illustrated compressor chamber 40 flowsaxially through the inlet opening 42, is propelled generally radiallyinto the volute portion 40 a, and then directed along a generallycircular path to the outlet opening 46.

As shown in FIG. 4, the case section 36 presents a circular recess 48for purposes which will be described. In addition, the section 36presents an outwardly projecting lip 50 that extends partly around theperimeter thereof (e.g., see FIGS. 2 and 4). The lip 50 is received in acomplemental groove 52 defined in the case section 34, and a pluralityof fastener assemblies 54 serve to secure the case sections 34 and 36 toone another. As particularly shown in FIG. 4, each of the fastenerassemblies 54 preferably includes a threaded screw 56 received in thecase section 34 and a washer 58 pressed against the lip 50.

The middle case section 36 also cooperates with the case section 38 todefine a transmission chamber 60 (see FIGS. 3 and 4). As particularlyshown in FIG. 3, the transmission chamber 60 is preferably teardropshaped, with the bottom being wider than the top. An impeller shaftopening 62 that is concentric with the inlet opening 42 extends throughthe case section 36 from the compressor chamber 40 to the transmissionchamber 60. A set of internally threaded passageways 64,65,66 alsoextend through the case section 36, with each of the passageways64,65,66 normally being sealed by a respective threaded plug 68,69,70.Except for the shaft opening 62 and the passageways 64,65,66, thechambers 40 and 60 are otherwise separated from one another by the casesection 36. Defined in the case sections 36 and 38 in axial alignmentwith the shaft opening 62 are a pair of opposed bearing assembly sockets72 and 74. An inwardly projecting dividing wall 76 is located along theshaft opening 62 to present a seal recess for purposes which will bedescribed.

The case section 38 similarly includes an input shaft opening 78 that isspaced upwardly from the bearing assembly socket 74. Similar to theimpeller shaft opening 62, the input shaft opening 78 is axially alignedwith opposed bearing assembly sockets 80 and 82 defined in the casesections 36 and 38. There is likewise an inwardly projecting dividingwall 84 alongside the bearing assembly socket 82 to present a sealrecess as will be described. In the preferred embodiment, a pair ofopposed, relatively small bearing assembly sockets 86 and 88 defined inthe case sections 36 and 38 are utilized, although two additional pairsof sockets 90 and 92 (only the sockets defined in the case section 36being shown in FIG. 3) are provided in the transmission chamber 60. Thethree pairs of sockets permit the supercharger to be mounted at variousangles, while ensuring sufficient and effective dispersion oflubrication fluid within the transmission chamber 60. It is noted thatthe passageway 66 projects from the center socket 86 (see FIG. 4).

An endless O-ring 94 retained within a continuous groove defined in thecase section 36 provides a seal between the case sections 36 and 38 (seeFIG. 4). A pair of alignment rods 96 and 98 (see FIG. 3) ensure properpositioning of the case sections 36 and 38 relative to one another, aswell as a series of attachment screws 100 (see also FIG. 2).

As particularly shown in FIG. 2, the illustrated case section 38presents a finned outer face 102 for promoting heat exchange between thetransmission chamber, particularly the lubrication fluid, andatmosphere. The outer face 102 is also provided with a plurality ofmounting bosses 104, each being tapped so that a mounting bolt (notshown) may be threaded therein to fasten the supercharger 20 to amounting bracket (also not shown) fixed to the engine 22.

In the usual manner, the supercharger 20 includes a rotatable impeller106 located within the compressor chamber 40 (see FIG. 4). The impeller106 is preferably machined from a billet of 7075 T-6 aircraft aluminum,although other suitable materials (e.g., cast aluminum) may be used. Itis further preferred to use the impeller commercially available from theassignee of record of the invention claimed herein. However, theimpeller 106 may be variously configured without departing from thespirit of the present invention. With respect to the preferredembodiment, the impeller 106, regardless of its design, induces andcauses fluid to flow through the compressor chamber 40 as hereinabovedescribed. It is particularly noted that the impeller 106 is providedwith a central mounting hole 108. In addition, the impeller 106 has acircular, solid base 110 that spans and is received in the recess 48.

The impeller 106 is drivingly connected to the belt drive 26 of theengine 22 by a transmission 112 located generally in the transmissionchamber 60. The transmission 112 may be variously configured but atleast some component(s) thereof preferably require(s) continuouslubrication during operation.

As discussed in detail below, in the preferred embodiment, thetransmission 112 includes an impeller shaft 114 rotatably supported by apair of bearing assemblies 116 and 118 press fit within the respectivesockets 72 and 74. In the usual manner, a wavy spring washer 120 isprovided in at least one of the sockets 72 and 74. As will be described,the bearing assemblies 116 and 118 have an inventive construction thatserves to extend bearing life without sacrificing speed of the shaft114, cost or simplicity in construction.

The illustrated impeller shaft 114 projects through the opening 62 andinto the compressor chamber 40. The mounting hole 108 of the impeller106 receives the end of the shaft 114 therein, with the impeller 106preferably being pressed onto the shaft 114 and retained thereon by acap 122. It is noted that the cap 122 is secured in place by a screw 124threaded into an axial bore 126 of the shaft 114. In the illustratedembodiment, the shaft 114 presents a cantilevered section (i.e., theportion of the shaft 114 projecting leftwardly beyond the bearingassembly 116 when viewing FIG. 4) on which the impeller 106 is mounted.However, it is entirely within the ambit of the present invention toalternatively support the impeller shaft 114 on both sides of theimpeller 106. For example, a suitable alternative construction mightinvolve lengthening the impeller shaft so that it projects beyond theimpeller and providing a bearing assembly in the compressor chamberbetween the shaft and case.

When it is desired to remove the impeller 106 from the shaft 114, theouter case section 34 is detached from the middle case section 36 andthe retaining screw 124 and cap 122 are removed. The plugs 68,69,70 arealso unscrewed from their respective passageways 64,65,66. A tool maythen be inserted through one or all of the passageways 68,69,70 toengage the impeller base 110 and force the impeller 106 off the end ofthe shaft 114. This might require a significant removal force becausethe impeller 106 is preferably press fit onto the shaft 114.

The impeller shaft 114 is preferably machined to present a pinion 128located between the bearing assemblies 116 and 118. The pinion 128intermeshes with a relatively larger gear 130 supported by an inputshaft 132. The gear 130 is preferably keyed to the shaft 132, althoughthese components maybe fixedly interconnected in any other suitablemanner. Similar to the impeller shaft 114, a pair of bearing assemblies134 and 136 press fit within respective ones of the sockets 80 and 82rotatably support the input shaft 132. Additionally, a wavy springwasher 138 is provided in the socket 82 adjacent the dividing wall 84.The input shaft 132 projects through the shaft opening 78 and beyond theouter face 102 of the case section 38. The belt drive 26 includes adriven sheave 140 keyed to the outwardly projecting portion of the inputshaft 132. The driven sheave 140 is further retained on the shaft 132 bya screw 142 threaded into an axial bore 144 of the shaft 132. Theillustrated belt drive 26 further includes a drive sheave 146 fixed tothe crank shaft 24, a belt 148 entraining the sheaves 140 and 146, andan idler sheave 150 suitably tensioning the belt 148. Thus, rotation ofthe crank shaft 24 effects rotation of the impeller 106.

Those ordinarily skilled in the art will appreciate that the gear-typetransmission 112 of the preferred embodiment produces noise that isnoticeably greater than a belt drive. It has been determined that theimpeller 106 actually amplifies the noise of the transmission 112, andthe noise typically associated with a gear driven supercharger isnormally considered undesirable. In this regard, the impeller shaft 114may be designed to dampen noise that might otherwise propagate throughthe shaft 114 to the impeller 106. Such a shaft construction isdisclosed in filed application for U.S. patent Ser. No. 09/669,018,Filed Sep. 22, 2000, entitled GEAR DRIVEN SUPERCHARGER HAVING NOISEREDUCING IMPELLER SHAFT, which is hereby incorporated by referenceherein as is necessary for a full and complete understanding of thepresent invention.

The pinion 128 is significantly smaller than the drive gear 130 so thatthe transmission provides a significant step up in rotational speedbetween the input shaft 132 and impeller shaft 114. For example, duringregular operation of the supercharger 20, the illustrated shaft 114 andpinion 128 will reach speeds of up to 30,000 to 70,000 rpm. A suitablepinion 128 diameter is approximately 1.2 inches, with the drive gear 130being about three times that size.

Because lubrication fluid will be dispersed throughout the transmissionchamber 60 in the manner described below, seal assemblies 152 and 154are provided at the shaft openings 62 and 78, respectively. Turningfirst to the impeller shaft seal assembly 152, a retaining ring 156maintains a seal 158 against the dividing wall 76. The seal 158 isprovided with a circumferential O-ring 160 that sealingly engages thecase section 34. The seal 158 is formed of any suitable material, suchas that available under the designation “TEFLON”, and preferablyprovides double or redundant sealing contact with a seal surface 161 ofthe impeller shaft 114. On the other hand, the input shaft seal assembly154 includes a metal case 162 press fit within the case section 38against the dividing wall 84. The case 162 houses a rubber seal 164 thatis sealingly retained between the input shaft 132 and case 162 by aspring 166. The illustrated seal assemblies 152 and 154 are preferredbut shall be considered as illustrative only, and the principles of thepresent invention are equally applicable to a supercharger using variousother types of seals.

A lubricant slinging disc 170 projects into the reservoir portion so asto be partly submerged in the lubricant. The illustrated disc 170includes an outer toothed edge 172 that intermeshes with the pinion 128so that the disc 170 is rotated by the transmission 112. Such anarrangement is disclosed in filed application for U.S. patent Ser. No.09/668,223, Filed Sep. 22, 2000, entitled CENTRIFUGAL SUPERCHARGERHAVING LUBRICATING SLINGER, which is hereby incorporated by referenceherein as is necessary for a full and complete understanding of thepresent invention. As shown in FIG. 4, the disc 120 is suitably fixed(i.e., press fit) to a shaft 174 and positioned between a pair ofbearing assemblies 176 and 178 by respective spacers 180 and 182. Thebearing assemblies 176 and 178 are press fit within respective ones ofthe sockets 86 and 88 and thereby serve to rotatably support the shaft174 and disc 170 within the transmission chamber 60. As with the othershaft assemblies, a wavy spring washer 184 is provided in the socket 88adjacent the bearing assembly 178.

As noted in the incorporated application, the disc 170 creates a highlydesirable lubricating mist within the transmission chamber 60. The mistensures that the transmission components (i.e., the gears 128,130 andthe bearing assemblies 116,118,134,136) are adequately lubricatedwithout creating undesirable hydraulic separation forces.

However, the principles of the present invention are equally applicableto various other supercharger lubrication systems. That is, the presentinvention is preferably utilized with a self-contained superchargerhaving a partly filled transmission chamber, although the inventivefeatures can be employed in a supercharger using an outside lubricationsource or a supercharger having a fully filled transmission chamber. Forexample, it is entirely within the ambit of the present invention tolubricate the transmission with engine lubricant or a recirculatinglubrication system dedicated to the supercharger. The alternativesupercharger may also include wicks or jet sprayers, rather than theslinging disc 170, for directing lubricant to the transmissioncomponents.

It is again noted, however, that the illustrated lubrication system ismost preferred because a failure of the transmission 112 (e.g., metalfragments produced by broken gear teeth, shaft failures, etc.) do notdamage the engine 20. It is further noted that any one of the bearingassemblies 116,118,134,136,176,178 maybe pre-lubricated such thatlubrication during operation is unnecessary.

Those ordinarily skilled in the art will appreciate that because theshaft 114 is required to rotate at extremely high speeds in order toproduce the desired boost, achieving effective, durable rotationalsupport for the shaft 114 is problematic. The specified limits of ballbearing assemblies are commonly exceeded in conventional superchargerapplications thereby greatly increasing the risk of premature bearingfatigue and a reduced life span of the supercharger.

Responsive to these problems, the present invention utilizes a multiplebearing arrangement in each of the bearing assemblies 116 and 118. Itwill be appreciated that the bearing assemblies 116 and 118 arevirtually mirror images of one another.e Thus, for the sake of brevity,only the assembly 116 received in the socket 72 will be detailedlydescribed herein with the understanding that the assembly 118 issimilarly constructed. The multiple bearing arrangement includes a shaftbearing 190 and a case bearing 192. As illustrated, each of the bearings190 and 192 may essentially comprise a standard ball bearing assembly.The bearings 190 and 192 are staged, i.e. arranged to share theresponsibility of rotatably supporting the shaft 114 on the casesections 36 and 38. That is to say, the bearings 190 and 192 areintercoupled by a spacer 194 in such a manner that the entire velocityvariance between the shaft 114 and case 32 (e.g., 350 ft./sec vs. therelatively stationary case) is shared by two bearing assemblies. It isbelieved that this configuration maintains the variable velocities ofthe bearing components within each bearing in tolerable ranges, eventhough the overall velocity variance between the shaft and the case areabove most bearing assembly operational limitations.

Turning now to FIG. 5, the shaft bearing 190 includes an inner race 196.The inner race 196 is fixed relative to the shaft 114. The inner race196 must be dimensioned to allow the shaft bearing 190 to be press fitonto the journal portion of the shaft 114. In the preferred embodimentthe inner race 196 is cylindrical in shape, matching the cylindricalshape of the journal portion of the shaft 114. The inside diameter ofthe inner race 196 is just slightly greater than the outside diameter ofthe journal portion of the shaft 114. The inner race 196 of the shaftbearing 190 could be any size and shape so long as it sufficientlymatches the shape and size of the journal portion of the shaft 114 toallow the inner race 196 to be fixed relative to the shaft 114. Theinner race 196 must also be configured to allow cooperation with theother components of the bearing assembly 116 to provide adequaterotational support of the shaft 114. Although the preferred embodimentutilizes a press fit as the means to fix the inner race 196 relative tothe shaft 114, any method of sufficiently affixing the inner race 196 tothe shaft 114 could be implemented (e.g., the inner race couldalternatively be machined as an integral part of the shaft).

The shaft bearing 190 further includes an outer race 198. The outer race198 matches the shape of the inner race 196 and in the preferredembodiment is cylindrically shaped. In the preferred embodiment, thediameter of the outer race 198 is greater than the diameter of the innerrace 196 and is defined in the same radial plane relative to the shaft.The diameter of the outer race 196 defines an exterior dimension for theshaft bearing 190, the relevance of which will become apparent asdiscussed below. However, the terms “inner” and “outer” as used hereinto describe the preferred embodiment were selected to facilitate clarityof the description and do not necessarily describe relative radialpositions. For example, it is well within the ambit of the presentinvention that the inner and outer races could be configured so that theinner race is positioned, or at least a portion thereof, radiallyoutward (relative to rotational axis of the shaft) from part or all ofthe outer race.

Interposed between the inner race 196 and the outer race 198 is shaftbearing ball ring 200. The ball ring 200 includes shaft bearing balls202 and a shaft bearing cage (not shown). Each of the races 196 and 198includes a curvilinear groove 204, with the grooves 204 cooperativelydefining a circular opening in which the ring 200 is received. The innerrace 196 and outer race 198 must be dimensioned to allow the balls 202to contact the inner race 196 and the outer race 198 along the grooves204 for rotational support of the shaft 114. The balls 202 run in thecurvilinear grooves 204 of the races 196 and 198 and generally define aradial plane relative to the shaft 114. The cage is configured toseparate the balls 202 and maintain even spacing between the balls 202in order to prevent the balls 202 from touching one another. The balls202 and races 196 and 198 can be constructed of any material thatprovides the desired rotational support of the shaft 114, rotationalspeed and bearing life, for example high-carbon chromium steel 52100heat treated to high strength and hardness and smoothly ground andpolished.

Similar to the shaft bearing 190, the case bearing 192 includes innerrace 206, outer race 208 and ball ring 210 interposed between the innerrace 206 and the outer race 208. Subject to the differences describedbelow, the case bearing inner and outer races 206 and 208 and the ballring 210 are configured in the same manner as the shaft bearing innerand outer races 196 and 198 and the ball ring 200. That is to say, thecase bearing ball ring 210 includes case bearing balls 212 that run incurvilinear grooves 214 of the races 206 and 208 and generally define aradial plane relative to the shaft 114. Although not shown, the casebearing ball ring 210 also includes a cage for separating the balls 212.In the preferred embodiment, the races 206 and 208 are cylindricallyshaped with the diameter of the outer race 208 being greater than thediameter of the inner race 206. In the preferred embodiment, the radiiof the case bearing balls 212 are greater than the radii of the shaftbearing balls 202, although the principles of the present invention arenot limited to this size relationship.

The case bearing inner race 206 is fixed relative to the shaft bearingouter race 198. In the preferred embodiment, the case bearing inner race206 and shaft bearing outer race are fixed to the spacer 194 (see FIG.5). The spacer 194 has a tubular configuration, dimensioned to fitcontiguously between the inner race 206 of the case bearing 192 and theouter race 198 of the shaft bearing 190. One advantage of utilizing thespacer 194 is that it allows common commercially manufactured bearingsto be used for the shaft bearing 190 and the case bearing 192. That isto say, these bearings do not have to be specially manufactured tospecification, but rather the spacer 194 need only be machined anddimensioned to accommodate the pre-manufactured dimensions of the shaftbearing 190 and the case bearing 192. The diameter of the case bearinginner races 206 defines an interior dimension. In the preferredembodiment, the interior dimension of the case bearing 192 is greaterthan the exterior dimension of the shaft bearing 190. In addition, inthe preferred embodiment, the radial planes defined by the shaft bearingball ring 200 and the case bearing ball ring 210 are coplanar (see FIG.5). That is to say, the shaft bearing 190 and the case bearing 192 areconcentrically positioned relative to one another. In this way, thespacer 194 can be dimensioned to allow common commercially availableball bearings to be fixed together relatively easily and inexpensively.As will become apparent from the discussion below, neither the relativesizes of the interior and exterior dimensions, the use of a separatespacer 194, nor the coplanar configuration of the ball rings 200 and 210are critical to the present invention, and these features could take onmany different configurations.

The case bearing outer race 208 is fixed relative to the case 32. It isbelieved this staged bearing arrangement—i.e. the inner race 196 of theshaft bearing 190 fixed relative to the shaft 114, the outer race 208 ofthe case bearing 192 fixed relative to the case 32 and the outer race198 of the shaft bearing 190 fixed relative to the inner race 206 of thecase bearing 192—provides the bearing assembly 116 with overallsynergistic benefits that either a single bearing or unstaged bearingcombinations cannot provide. That is to say, it is believed that theexploitation of any one advantage in a single bearing or unstagedcombination is often limited by a similar reduction of anotheradvantage. That is, exploiting a beneficial design characteristic in atraditional single bearing or unstaged bearing combination typicallyinvolves another beneficial design characteristic to be sacrificed. Inthe staged bearing arrangement, one bearing could be designed to exploitone advantage over another—for example the shaft bearing 190 could bedesigned to withstand a large radial load at a thrust at the expense oflowering the rotational speed at which the shaft balls 202 losestabilization and start to skid along the pitch line. At the same time,the other bearing could be designed to take advantage of what wassacrificed in the first bearing—for example, the case bearing 192 couldbe designed to maintain its stabilization point at very high rotationalspeeds. Accordingly, the staged bearing arrangement of the previousexample could both withstand a large radial load at a thrust andmaintain its stabilization point at very high rotational speeds. It isfurther believed that this staged bearing arrangement also reduces thevariances in the velocities of the balls 202 and 212 at the outerperiphery—for example along the pitch line—relative to the velocity ofthe balls 202 and 212 at their centers. It is believed that reducingthese variances also reduces the points of friction—or skidding—of theballs 202 and 212 relative to the races and cages, thereby increasingthe overall life of the bearing assembly 116.

As previously discussed, the bearing assembly 118 is a virtual mirrorimage of the bearing assembly 116. It will be understood that thebearing assembly 118, therefore, is similarly constructed as wasdetailedly described above regarding the bearing assembly 116.

It is noted that the principles of the present invention are equallyapplicable to multiple bearing arrangements utilized to rotatablysupport any shaft on a stationary body and are not just limited tosupercharger applications. In addition, the principles of the presentinvention are equally applicable to various other superchargerconfigurations and alternative multiple bearing arrangements. Forexample, the type of bearings utilized in the staged arrangement couldbe other than ball type bearings, including roller bearings (cylindricalor tapered), needle bearings, or journal bearings. Different types ofbearings could be staged together, for example, a ball bearing staged ina journal bearing. Certain features of the bearings implemented in thestaged arrangement could vary, for example, the bearings could bepre-lubricated bearings. The arrangement could utilize filling ornon-filling type bearings. The bearings could also include additionalfeatures, such as self-alignment or angular contact capabilities. Inaddition, the number of bearings that are staged (fixed relative to oneanother) could include more than two. Furthermore, the configuration ofthe bearing arrangement could take on many different alternative forms

One possible alternative to the configuration of the bearing arrangementis shown in FIG. 6. Particularly, the multiple bearing arrangementincludes a shaft bearing 300 and a case bearing 302. The bearings 300and 302 are configured very similar to the bearings 190 and 192 of thepreferred embodiment. However, in this alternative embodiment the shaftbearing ball ring 304 defines a general plane that is not coplanar withthe corresponding plane of the case bearing ball ring 306, but issignificantly offset therefrom. In addition, the exterior dimensiondefined by the diameter of the outer race 308 of the shaft bearing 300is greater than the interior dimension defined by the diameter of theinner race 310 of the case bearing 302. In this embodiment, the spacer312 is configured to correspond to the offset positioning of the shaftbearing 300. That is to say the spacer 312 has a generally tubular shapewith opposing ends of differing diametrical dimensions and a tieredcircumferential surface (see FIG. 6). The spacer 312 is dimensioned toallow the case bearing 302 and spacer 312 to have an inside diametersufficiently greater (at its smallest diametric span) than the outsidediameter of the shaft 314, thereby providing the necessary clearance tomount the bearing arrangement onto the shaft 314.

A second alternative to the configuration of the bearing arrangement isshown in FIG. 7. Particularly, the multiple bearing arrangement includesa shaft bearing 400 and a case bearing 402, configured in a mannersimilar to the bearings 190 and 192 of the preferred embodiment. In thisalternative embodiment, the shaft bearing includes dual inner races 404,dual outer races 406, and dual ball rings 408. As with the alternativeembodiment shown in FIG. 6, the dual ball rings 408 each define ageneral plane that is offset from the corresponding plane of the casebearing ball ring 410. In this alternative embodiment, the dual innerraces 404 are separated, or spaced apart from one another, and flank thecase bearing 402 (see FIG. 7). That is to say the case bearing 402 ispositioned between the two inner races 404. The dual outer races 406 andthe dual ball rings 408 are configured in a similar, flankingorientation, relative to the case bearing 402. The spacer 412 isconfigured in a manner similar to the spacer 312 of the previousalternative embodiment; however, the spacer 412 has a double tieredcircumferential surface corresponding to the dual outer races 406 of theshaft bearing 400 (see FIG. 7). The spacer 412 is fixed relative to bothof the dual outer races 406 of the shaft bearing 400 and fixed relativeto the inner race 414 of the case bearing 402.

A third alternative embodiment of the configuration of the bearingarrangement is shown in FIG. 8. In this embodiment, both the shaftbearing 500 and the case bearing 502 include dual components. That is,the shaft bearing 500 includes dual inner races 504, dual outer races506 and dual ball rings 508. Similarly, the case bearing 502 includesdual inner races 510, dual outer races 512 and dual ball rings 514. Aswith the previously discussed embodiments, the inner races 504 and 510,the outer races 506 and 512, and the ball rings 508 and 514 areconfigured in a manner similar to the configuration of thosecorresponding components in the preferred embodiment. Unlike theprevious alternative embodiments, however, the exterior dimensiondefined by the outer races 506 of the shaft bearing 500 is less than (soas to fit concentrically within) the interior dimension defined by theinner races 510 of the case bearing 502 (see FIG. 8). The shaft bearingball rings 508 each define a plane that is generally coplanar with theplane defined by the corresponding case bearing ball ring 514 (see FIG.8). The dual components of the case bearing 502 could also be configuredin a spaced apart orientation, similar to the dual components of theshaft bearing 400 of the alternative embodiment illustrated in FIG. 7.That is to say, the multiple bearing it arrangement could be configuredso the dual components of the case bearing 502 have a flankingorientation with the shaft bearing 500 positioned between the dualcomponents of the case bearing 502. The spacer 516 has a tubularconfiguration similar to the spacer 194 of the preferred embodiment;however, the spacer 516 has an axial dimension greater than the axialdimension of the spacer 194 to allow the spacer 516 to be fixed relativeto both of the outer races 506 of the shaft bearing 500 and to both ofthe inner races 510 of the case bearing 502.

A fourth alternative embodiment of the configuration of the bearingarrangement is shown in FIG. 9. This alternative embodiment has abearing arrangement similar to the arrangement illustrated in FIG. 7;however, in this embodiment the case bearing 600 has dual inner races602, dual outer races 604 and dual ball rings 606. The spacer 608 has adouble tiered circumferential surface similar to the configuration ofthe spacer 412 of the embodiment illustrated in FIG. 7; however, thespacer 608 has an axial dimension greater than the axial dimension ofthe spacer 412 to allow the spacer 608 to be fixed relative to both ofthe inner races 602 of the case bearing 600. Differing from theconstruction of the spacers of the previously discussed embodiments, thespacer 608 has a two-piece construction. That is to say, the spacer 608includes a first tube portion 610 and a second tube portion 612 (seeFIG. 9). Each of the tube portions 610 and 612 have a single tieredcircumferential surface similar to the configuration of the spacer 312of the embodiment illustrated in FIG. 6. The first tube portion 610 isfixed relative to the first outer race 614 of the shaft bearing 616 andfixed relative to both of the dual inner races 602 of the case bearing600 (see FIG. 9). The second tube portion 612 is fixed relative to thesecond outer race 618 of the shaft bearing 616. Both of the tubeportions 610 and 612 are fixed relative to each other along thecircumferential surfaces having the smallest tier diameter. That is tosay the end of the second tube portion 612 opposing the second outerrace 618 fits into the end of the first tube portion 610 opposing thefirst outer race 614. The exterior circumferential surface of the secondtube portion 612 is fixed relative to (and contiguous with) the interiorcircumferential surface of the first tube portion 610.

All of the embodiments previously discussed utilize some form of aspacer that is separate and distinct from the bearings interconnect therespective components of the shaft and case bearings. However, the shaftbearing and the case bearing can also be fixed together utilizingvarious alternative spacer designs or directly affixing the two bearingstogether without implementing a spacer. One alternative design is shownin FIG. 10, wherein the race of the shaft bearing 700 and the inner raceof case bearing 702 are integrally formed (e.g., machined as a unitarybody 704. That is to say, the body 704 includes an inner groove 706 andan outer groove 708.

The preferred forms of the invention described above are to be used asillustration only, and should not be utilized in a limiting sense ininterpreting the scope of the present invention. Obvious modificationsto the exemplary embodiments, as hereinabove set forth, could be readilymade by those skilled in the art without departing from the spirit ofthe present invention.

The inventor hereby states his intent to rely on the Doctrine ofEquivalents to determine and assess the reasonably fair scope of thepresent invention as pertains to any apparatus not materially departingfrom but outside the literal scope of the invention as set forth in thefollowing claims.

What is claimed is:
 1. A centrifugal supercharger for supplyingsupercharged intake fluid to an engine; said centrifugal superchargercomprising: a case; a rotatable impeller operable to supercharge theintake fluid; an impeller shaft on which the impeller is supported, saidimpeller shaft being drivingly connectable to a power source; and amultiple bearing arrangement rotatably supporting the impeller shaft onthe case, said bearing arrangement including a shaft bearing and a casebearing, each of which includes relatively rotatable first and secondraces, said first race of the shaft bearing being fixed relative to theimpeller shaft, said second race of the case bearing being fixedrelative to the case, and said second race of the shaft bearing andfirst race of the case bearing being fixed relative to one another.
 2. Acentrifugal supercharger as claimed in claim 1, each of said bearingsincluding a ball ring interposed between the first and second racesthereof, said ball rings including a plurality of balls moveablyinterposed between said first and second races, and a cage associatedwith the balls and operable to separate the balls, said ball rings eachdefining a plane associated therewith.
 3. A centrifugal supercharger asclaimed in claim 2, said shaft bearing balls having a common diameterthat is less than the common diameter of the case bearing balls.
 4. Acentrifugal supercharger as claimed in claim 2, said planes beingcoplanar.
 5. A centrifugal supercharger as claimed in claim 2, saidplanes being offset.
 6. A centrifugal supercharger as claimed in claim1, said second race of the shaft bearing and the first race of the casebearing being integrally formed as a unitary body.
 7. A centrifugalsupercharger as claimed in claim 1, said bearing arrangement including aspacer fixed relative to both the second race of the shaft bearing andthe first race of the case bearing.
 8. A centrifugal supercharger asclaimed in claim 1, said first race of the case bearing presenting aninterior dimension, said second race of the shaft bearing presenting anexterior dimension that is greater than said interior dimension.
 9. Acentrifugal supercharger as claimed in claim 1, at least one of thebearings including an additional first race and an additional secondrace, said additional first race being fixed relative to the samestructure as the first-mentioned first race of said at least one of thebearings, said additional second race being fixed relative to the samestructure as the first-mentioned second race of said at least one of thebearings.
 10. A centrifugal supercharger as claimed in claim 9, saidadditional races being spaced from the first-mentioned races of said atleast one of the bearings, said other bearing being located between thespaced apart additional and first mentioned races.
 11. A centrifugalsupercharger as claimed in claim 1, each of said bearings beingconfigured so that the first race thereof is spaced radially inward fromthe second race thereof.
 12. A centrifugal compressor as claimed inclaim 1, said impeller shaft presenting an outer surface speed at thefirst race of the shaft bearing of at least about 10,000 feet perminute.
 13. In a powered vehicle including an engine, an improvedsupercharger for supplying supercharged intake fluid to the engine, saidcentrifugal supercharger comprising: a case presenting a compressorchamber defined between an outlet opening connected to the engine and aninlet opening; a rotatable impeller in the compressor chamber, with theimpeller being operable to supercharge the intake fluid and force thesupercharged intake fluid through the outlet opening when rotated; animpeller shaft on which the impeller is supported, said impeller shaftbeing drivingly coupled to the engine; and a multiple bearingarrangement rotatably supporting the impeller shaft on the case, saidbearing arrangement including a shaft bearing and a case bearing, eachof which includes relatively rotatable first and second races, saidfirst race of the shaft bearing being fixed relative to the impellershaft, said second race of the case bearing being fixed relative to thecase, and said second race of the shaft bearing and first race of thecase bearing being fixed relative to one another.
 14. In a poweredvehicle as claimed in claim 13, each of said bearings including a ballring interposed between the first and second races thereof, said ballrings including a plurality of balls moveably interposed between saidfirst and second races, and a cage associated with the balls andoperable to separate the balls, said ball rings each defining a planeassociated therewith.
 15. In a powered vehicle as claimed in claim 14,said shaft bearing balls having a common diameter that is less than thecommon diameter of the case bearing balls.
 16. In a powered vehicle asclaimed in claim 14, said planes being coplanar.
 17. In a poweredvehicle as claimed in claim 14, said planes being offset.
 18. In apowered vehicle as claimed in claim 13, said second race of the shaftbearing and the first race of the case bearing being integrally formedas a unitary body.
 19. In a powered vehicle as claimed in claim 13, saidbearing arrangement including a spacer fixed relative to both the secondrace of the shaft bearing and the first race of the case bearing.
 20. Ina powered vehicle as claimed in claim 13, said first race of the casebearing presenting an interior dimension, said second race of the shaftbearing presenting an exterior dimension that is greater than saidinterior dimension.
 21. In a powered vehicle as claimed in claim 13, atleast one of the bearings including an additional first race and anadditional second race, said additional first race being fixed relativeto the same structure as the first-mentioned first race of said at leastone of the bearings, said additional second race being fixed relative tothe same structure as the first-mentioned second race of said at leastone of the bearings.
 22. In a powered vehicle as claimed in claim 21,said additional races being spaced from the first-mentioned races ofsaid at least one of tie bearings, said other bearing being locatedbetween the spaced apart additional and first mentioned races.
 23. In apowered vehicle as claimed in claim 13, each of said bearings beingconfigured so that the first race thereof is spaced radially inward fromthe second race thereof.
 24. In a powered vehicle as claimed in claim13, said impeller shaft presenting an outer surface speed at the firstrace of the shaft searing of at least about 10,000 feet per minute. 25.In a powered vehicle as claimed in claim 24; a transmission drivinglyconnected to the engine so as to provide driving power to the impeller,with the impeller shaft being part of the transmission; and a drivemechanism drivingly connecting the transmission to the engine, saiddrive mechanism and said transmission being configured to rotate theimpeller shaft at said outer surface speed during operation of theengine.
 26. In a powered vehicle as claimed in claim 25, said drivemechanism comprising a belt drive including a plurality of sheaves andan endless belt drivingly connecting the sheaves.
 27. A centrifugalsupercharger for supplying supercharged intake fluid to an engine, saidcentrifugal supercharger comprising: a case; a rotatable impelleroperable to supercharge the intake fluid; an impeller shaft including acantilevered section on which the impeller is supported, said impellershaft being drivingly connectable to a power source; and a compoundbearing assembly rotatably supporting the impeller shaft on the case,said bearing assembly including a shaft bearing and a case bearing, eachof which includes relatively rotatable first and second races, saidfirst race of the shaft bearing being fixed relative to the impellershaft, said second race of the case bearing being fixed relative to thecase, and said second race of the shaft bearing and first race of thecase bearing being fixed relative to one another.
 28. A centrifugalsupercharger as claimed in claim 27, each of said bearings including aball ring interposed between the first and second races thereof, saidball rings including a plurality of balls moveably interposed betweensaid first and second races, and a cage associated with the balls andoperable to separate the balls, said ball rings each defining a planeassociated therewith.
 29. A centrifugal supercharger as claimed in claim28, said shaft bearing balls having a common diameter that is less thanthe common diameter of the case bearing balls.
 30. A centrifugalsupercharger as claimed in claim 28, said planes being coplanar.
 31. Acentrifugal supercharger as claimed in claim 28, said planes beingoffset.
 32. A centrifugal supercharger as claimed in claim 27, saidsecond race of the shaft bearing and the first race of the case bearingbeing integrally formed as a unitary body.
 33. A centrifugalsupercharger as claimed in claim 27, said bearing arrangement includinga spacer fixed relative to both the second race of the shaft bearing andthe first race of the case bearing.
 34. A centrifugal supercharger asclaimed in claim 27, said first race of the case bearing presenting aninterior dimension, said second race of the shaft bearing presenting anexterior dimension that is greater than said interior dimension.
 35. Acentrifugal supercharger as claimed in claim 27, at least one of thebearings including an additional first race and an additional secondrace, said additional first race being fixed relative to the samestructure as the first-mentioned first race of said at least one of thebearings, said additional second race being fixed relative to the samestructure as the first-mentioned second race of said at least one of thebearings.
 36. A centrifugal supercharger as claimed in claim 35, saidadditional races being spaced from the first-mentioned races of said atleast one of the bearings, said other bearing being located between thespaced apart additional and first-,mentioned races.
 37. A centrifugalsupercharger as claimed in claim 27, each of said bearings beingconfigured so that the first race thereof is spaced radially inward fromthe second race thereof.
 38. A centrifugal supercharger as claimed inclaim 27, said impeller shaft presenting an outer surface speed at thefirst race of the shaft bearing of at least about 10,000 feet perminute.
 39. In a powered vehicle including an engine, an improvedsupercharger for supplying supercharged intake fluid to the engine, saidcentrifugal supercharger comprising: a case presenting a compressorchamber defined between an outlet opening connected to the engine and aninlet opening; a rotatable impeller in the compressor chamber, with theimpeller being operable to supercharge the intake fluid and force thesupercharged intake fluid through the outlet opening when rotated; animpeller shaft including a cantilevered section on which the impeller issupported, said impeller shaft being drivingly coupled to the engine;and a compound bearing assembly rotatably supporting the impeller shafton the case, said bearing assembly including a shaft bearing and a casebearing, each of which includes relatively rotatable first and secondraces, said first race of the shaft bearing being fixed relative to theimpeller shaft, said second race of the case bearing being fixedrelative to the case, and said second race of the shaft bearing andfirst race of the case bearing being fixed relative to one another. 40.In a powered vehicle as claimed in claim 39, each of said bearingsincluding a ball ring interposed between the first and second racesthereof, said ball rings including a plurality of balls moveablyinterposed between said first and second races, and a cage associatedwith the balls and operable to separate the balls, said ball rings. eachdefining a plane associated therewith.
 41. In a powered vehicle asclaimed in claim 40, said shaft bearing balls having a common diameterthat is less than the common diameter of the case bearing balls.
 42. Ina powered vehicle as claimed in claim 40, said planes being coplanar.43. In a powered vehicle as claimed in claim 40, said planes beingoffset.
 44. In a powered vehicle as claimed in claim 39, said secondrace of the shaft bearing and the first race of the case bearing beingintegrally formed as a unitary body.
 45. In a powered vehicle as claimedin claim 39, said bearing arrangement including a spacer fixed relativeto both the second race of the shaft bearing and the first race of thecase bearing.
 46. In a powered vehicle as claimed in claim 39, saidfirst race of the case bearing presenting an interior dimension, saidsecond race of the shaft bearing presenting an exterior dimension thatis greater than said interior dimension.
 47. In a powered vehicle asclaimed in claim 39, at least one of the bearings including anadditional first race and an additional second race, said additionalfirst race being fixed relative to the same structure as thefirst-mentioned first race of said at least one of the bearings, saidadditional second race being fixed relative to tide same structure asthe first-mentioned second race of said at least one of the bearings.48. In a powered vehicle as claimed in claim 47, said additional racesbeing spaced from the first-mentioned races of-said at least one of thebearings, said other bearing being located between the spaced apartadditional and first-mentioned races.
 49. In a powered vehicle asclaimed in claim 39, each of said bearings being configured so that thefirst race thereof is spaced radially inward from the second racethereof.
 50. In a powered vehicle as claimed in claim 39, said impellershaft presenting an outer surface speed at the first, race of the shaftbearing of at least about 10,000 feet per minute.
 51. In a poweredvehicle as claimed in claim 50, a transmission drivingly connected tothe engine so as to provide driving power to the impeller, with theimpeller shaft being part of the transmission; and a drive mechanismdrivingly connecting the transmission to the engine, said drivemechanism and said transmission being configured to rotate the impellershaft at said outer surface speed during operation of the engine.
 52. Ina powered vehicle as claimed in claim 51, said drive mechanismcomprising a belt drive including a plurality of sheaves and an endlessbelt drivingly connecting the sheaves.